An arc-flash is a dangerous event in which a flashover of electrical current leaves its intended path and travels through the air from one conductor to another, or to ground. The result of an arc-flash incident is often a violent explosion, and when a person is in close proximity, can lead to serious injury or death. This possibility of arc-flash incidents creates a serious safety hazard
Certain conditions, such as arcing, tracking, and corona, which produce the potential for arc-flash, can be detected before creating flashover or arc-flash incidents. Arcing, tracking, and corona emissions produce ionization. Ionization is a process by which a neutral atom or molecule loses or gains an electron(s), thereby acquiring a net charge, becoming an ion. Ionization has by-products: ozone and nitrogen oxides. These combine with moisture to produce nitric acid, which is destructive to most dielectrics and certain metallic compositions, resulting in corrosion. The object of electric condition monitoring is to detect the presence of these events before flashover occurs or before they produce an arc-flash incident when a cabinet is opened.
There have been attempts to detect these conditions. For example, infrared thermography detects heat generated by arcing and in most instances tracking; however, these types of detection systems will not sense corona. If cabinets housing the electrical equipment are enclosed, unless there is an IR test port, it is highly unlikely that infrared will detect the presence of these emissions. In addition, to view components within enclosed electrical cabinets, it is necessary to conform to National Fire Protection Agency (“NFPA”) standards with regard to personal protective equipment (“PPE”); therefore, in many situations IR inspectors must wear cumbersome clothing and hoods and perform the required procedure to open cabinets for inspection. This can be very time consuming and, in hot weather, very uncomfortable.
While a great majority of the inspections around energized electrical equipment incorporate portable instruments, these inspections are limited in their ability to protect equipment from failure or from an arc-flash potential going undetected. The limitations are time based. If an inspector is testing at the time any of these incidents is occurring, there is a good chance they will be detected and reported for corrective action. But, unlike mechanical conditions which are usually detected first and then trended to specific action levels, once arcing, tracking, or corona are present, there is a potential for failure and arc flash that can occur at any time.
Therefore, there is a need for continuous on-line monitoring of enclosed electrical equipment. Ultrasound technology is ideally suited for detecting these emissions since the ionization process produces frequencies in the ultrasonic region. Ultrasonic instruments sense between 20-100 kHz and use heterodyning to translate the ultrasonic emissions into the audible range. These portable instruments provide information via headphones for the audio signal and on a meter to display intensity readings, usually in decibels. These hand-held devices often contain two sensing heads containing piezoelectric transducers: a scanning module for airborne sounds and a contact probe/wave-guide for structure borne signals.
In some embodiments, an electrical cabinet monitor or sensor is mounted on the internal side of a door or wall facing the components. Utilizing an airborne scanner, a threshold level can be set. If an event of arcing, tracking, or corona occurs, the sound level will be above the ambient threshold and be detected. An analog signal from the sensor is converted to a digital signal which is processed by the monitoring module executing on a computer. On-line monitoring provides several advantages. For example, it is not operator dependent and will continuously monitor. Whenever a condition occurs to produce the potential for arc flash or flashover, it will be sensed and alarmed instantly through the monitoring module.
According to one aspect, the present disclosure provides a computerized monitoring system for detecting electrical equipment failure. The system includes a sensor that detects a sound level representative of ultrasonic emissions radiating from electrical equipment to be monitored. A computer system in communication with the sensor is programmed to determine whether the electrical equipment is experiencing one or more of arcing, tracking, or corona based on the sound level detected by the sensor. In some embodiments, the computer system continuously monitors for these conditions based on the sound level detected by the sensor.
Depending on the circumstances, the computer system could send an alert message via a communications network responsive to detecting that the electrical equipment has experienced one or more of arcing, tracking, or corona based on the sound level detected by the sensor. By way of example, the alert message could be an email or a text message. This alert message could be sent to a pre-determined group of recipients.
In some cases, the system could include a plurality of sensors each operatively associated with respective electronic equipment, which allows multiple electrical cabinets to be monitored by the system, even if the electrical equipment is remote from each other. If the computer system detects that the sound level detected by at least one of the plurality of sensors exceeds a threshold sound level, alert message could be sent via a communications network. Depending on the circumstances, the alert message could include an identification of which sensor of the plurality of sensors detected a sound level that exceeds the threshold sound level.
According to another aspect, this disclosure provides a computerized monitoring system for detecting electrical equipment failure. The system a sensor configured to detect a sound level representative of ultrasonic emissions radiating from electrical equipment to be monitored. An interface device is provided in communication with the sensor that converts the sound level into computer-readable data. The system includes a non-transitory computer-readable medium having a computer program code stored thereon. A processor is in communication with the computer-readable memory and the interface device. The processor is configured to carry out instructions in accordance with the computer program code. When the computer program code executes, the processor is able to establish a threshold sound level using the sensor. The processor continuously queries the sensor to determine a current sound level, which allows a determination of whether the current sound level exceeds the threshold sound level. If so, an alert message is sent.
According to yet another aspect, this disclosure provides a computerized method of monitoring for electrical equipment failure. The method includes a step of establishing a threshold sound level using a sensor configured to detect a sound level representative of ultrasonic emissions radiating from electrical equipment to be monitored. The threshold sound level is representative of the electrical equipment operating in good working order. The sensor is periodically queried to determine a current sound level using a computer. Next, a determination is made using a computer whether the electrical equipment is experiencing one or more of arcing, tracking, or corona by comparing the current sound level with the threshold sound level.
Additional features and advantages of the disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrated embodiment exemplifying the best mode of carrying out the disclosure as presently perceived. It is intended that all such additional features and advantages be included within this description and be within the scope of the disclosure.
Corresponding reference characters indicate corresponding parts throughout the several views. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principals of the invention. The exemplification set out herein illustrates embodiments of the invention, and such exemplification is not to be construed as limiting the scope of the invention in any manner.